Re: How can I selet rows which have 2 columns values cross equal?

On Mar 11, 2006, at 16:46 , Michael Glaesemann wrote:

> select t1.id as t1_id, t2.id as t2_id
> from test t1
> join test t2 on (t1.a = t2.b and t1.b = t2.a)
> where t1.a < t2.a;
> t1_id | t2_id
> -------+-------
>      4 |     7
>      1 |     2
> (2 rows)


Just a follow-up (mostly to myself): I've been toying with using  
natural joins recently, and here's the same query rewritten to use a  
natural join:

select id as t1_id, t2_id
from test t1
natural join (    select id as t2_id        , a as b        , b as a    from test    ) t2
where id < t2_id;
t1_id | t2_id
-------+-------     4 |     7     1 |     2
(2 rows)


Michael Glaesemann
grzm myrealbox com